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k oooo y mm o. KIRBY AUTOMATIC TELEPHONE. EXCHANGE SYSTEM Original Filed J me May 12, 1925.

Urns? Kzrb May 12, 1925.

O. KIRBY AUTOMATIC TELEPHONE EXCHANGE SYSTEM Original Filed June 19, 1909 s Shets-Sheet 2 May 12,1925. I

O. K|RBY' AUTOMATIC TELEPHONE EXCHANGE SYSTEM Original Filed June 19, 1909 3 Sheets-Sheet 5 IIIIIIIIIII lllllfllllll V mmnmm mun mmmmlliiiiiiiiiiiiii 7W2 v ma r Reissued May 12, 1925.

To all whom it may concern:

Be it known that I, OMER KIRBY, a citizen of the United States of America and resident of Chicago, Cook County, Illinois, -have invented a certain new and useful Improvement in Automatic Telephone-Ei change Systems, of which the following is a specification.

My invention relates to automatic or semi-automatic telephone exchange systems.

The object of my invention is the provi sion of a system in which no electrical impulses corresponding to the number of the called subscriber are transmitted by the calling subscriber.

My invention contemplates, therefore, a system in-which the electrical impulses for producing the numerical switching operations are transmitted over the line. circuit by mechanism at the exchange or central station, and in which devices responsive ,to these impulses are p ovided at the substations, whereby the automatic operation of I the switches at the exchange or central staproper time by the calling subscriber, each switch operating automatically until stopped at some point in the operation thereof corresponding to the digit of the called number, and each numerical switch tion is made therewith, so that the'only act required on the part of the calling subscriber isthc topping of the switch at the proper point in its operation. but each of the subscriber. one for each digit of the called number, alternating with the diil'ercnt numerical switching operations which occur at the exchange or central station.

It. also contemplates the prorision of a corresponding to the dill'erent digits of the circuit by devices at the-exchange oncentral station, eachsubstation being provided with a device responsive to such impulses, and with mechanism for stopping the device at the calling substation as soon as the switch 1 operating in synchronism therewith has reached the predetermined point lXl' ltS operation which will give the calling subscriber a connection in accordance with the called number.

UNITED STATES? V DMER KIBBY, -01? CHICAGO, ILLINOIS, ASSIGNOR '10 AUTOMATIC ELECTRIC COMRANY,

' OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

tion may be interrupted or stopped. at the operating automatically as soon as connec diflerent acts on the part of the calling" system in which the electrical impulses called number are transmitted over the line PATENT OFFICE.

AUTOMATIC TELEPHONEEXGHANGE SYSTEM.

Original No. 1,172,366, dated February 22, 1916, Serial No. 503,109, filed June 19, 1909. Application for reissue filedluly 3Q, 1920. Serial No. 400,257.

It further contemplates a system in which numerical switches, such as selectors or connectors, are so constructed that the mere selection of and connection with an idle switch of either kind will serve automatically to start the operation thereof, which operation will continue until interrupted by the mechanism at the calling substation,

which mechanism may be of any suitable character so far as this aspect of my invention is concerned. p

' It further contemplates a system in which the switches have vertical motion to select groups and rotary motion to connect with a line in any selected group. the su'bstations being provided with step-by-step switches that operate in synchronism with the vertical step-by-step operations ot all of the numerical switches. and which also operate in synchronisrn with the rotary stepdiy-step motions of the connectors or other switches for making the final connection with the called subscribers line.

It further contemplates a system in which the substations are provided with indicators. and with means at the exchange or central station for transmitting impulses for operating said indicators in synchronisinwith the numerical switches, such as selectors and connectors. whereby any calling subscriber may observe the progress of the call, each indicator operating once for each digit of the called number.

It further contemplates a system in which automatic trunking switches are employed, and in which the subscribers lines are. free from operating grounds at the substations thereof, means being provided for preventin; seizure of a trunk by the mere taking down of the "receiver at the calling substation, or by the operation of the switch hook, whereby a calling subscriber cannot undesirably monopolize a trunk b taking down his receiver and then waiting some time before doing the other things which are necessary for making the call.

It further contcuu'ilates a system in which the called subscriber may control the connection, and may, without releasing such connection. operate an alarm signal at the My invention also. contemplates certain novel features and details of construction In Figure 2 there is shown diagrammatically a connector switch'F of improved oon struction. At H there-is shown a central ringer generator, while at I a common busy signaling apparatus is represented.v To the line of substation A gjne switch C, which is like the line switch Figs. land 2 taken together represent the central ofiiee switching apparatus involved in establishing a connection between the subscribers stations A and A. In Fig. 2 is shown a central battery B having its positive terminal preferably grounded at G. The central oliice switching apparatus is of the general type shown in English Patent No. 26.301'of 1906, but with new arrangement and changes of circuits to adapt it to operate in connection with a two-wire system-that is, a system in which there is no ground connection at, the subscribers station. The line switches C and C and master switch D are modified forms of the switches disclosed in The W'estern Electrician of January 25. 1906. and the American Tele from the usual automatic substation.

phone Journal ofJune 6, 1908. The first selector E is of the same general mechanical construction as the selector switch shown in United States Letters Patent No. 815.321. granted March 13. 1906, to Keith, Erickson & Erickson, while the connector switch F (Fig. 2) is of the general form shown in United States Letters Patent No. 815.176, granted March 13. 1906, to Keith, Erickson & Erickson.

Figs. 3 and 4 area front and'top view,

' respectively. of the substation impulse-indieating device.

Fig. is a sectional end view of the impulse-indicating device, along the line 55 of Fig. 3.

The substation A is somewhat different It comprises the usual receiver 2, switch book,

3, induction coil 4 which is composed of the secondary winding 5 and the primary winding 6 in series with the transmitter 7. 'When the switch nook is 111 normal position the represented a first selector there is allotted the.

ringer 8,,in series with the condenser 9, is

however, provided a device for indicating the impulses to the calling subscriber in order that the central ofiice switches may con; trolled'and caused to operate according to the desired number. This indicating mechanism, shown in Figs. 3, 4; and 5, comprises a magnet .12 for operating the armature and pawl 13, which in turn, when the magnet energizes, rotates the ratchet wheel 14 one step, so that the pointer 15 moves over the seals. .,.To the ratchet wheel let there is escured the arm 16, to which latter there is fastened one end of a coil spring 17, the other endof which is secured to a pin. This spring 17 provides the means for restoring the ratchet wheel and pointer when the dog 18 is out of engagement with the teeth of the wheel 14. The push button '19 controls the switch hook, the springs 20, 21 and 22 and also; the dog 18, which latter maintains the ratchet wheel 14 in its advanced position. The switch hook is locked in its normal position by the catch 23, as shown at 162 at substation A (Fig. 2); but whenthe receiver is removed and the button19 pressed, the catch is carried out of its locking position and permits the switch hook to rise, whereby the spring 24 is carried from the spring 25 into contact with the spring 26. Also, the arm 27 upon the rod 28 carries the spring 21 from. the spring 22 into contact with the spring 20. thereby bridging the r sistance coil 29 (Fig. 1) across the line conductors 10 and 11. Furthermore. when the button 19 is'pressed, the member 30 engages the end of the lever 18*, moves the shaft 31, and carries the dog 18 out of contact with the ratchet teeth. In response to the tension of the spring 17 the wheel 14 returns to normal, thereby restoring the pointer 15 to Starting place on the scale.

A clearer understi u'lcling of my improved I system may be hadffrbm an explanation of its operation when a subscriber operates the tion. For example, it will be pointed out how the subscriber at substation A may operate the main ofiice switches to establish connection with the substation A (Fig. 2), the number of which is 220. As previously stated, in my present system there is no impulse-sending device at the subscribers station, the impulses being made at the central office, and the subscriber controlling the number thereof by means of a push button. 7

When the receiver is' removed from the a switch book no operation occurs; but when the button 19 1S pressed and released and:

the switch hook rises the primary circuit 115 central office switches to establish a connec- C. \Vhen this relay energizes a circuit is closed through 'the trip or plunger magnet. 33, which then operates to thrust'the plunger into a bank terminal and extend the calling line .conductors to the trunk conductors leading to the first selector switch E. hen

the line is extended to the selector E this switch operates automatically and independently of the subscriber to step the shaft, and shaft wipers in a vertical direction. means of the button 19, however, the su scriber controls the number of vertical impulses, and when the pointer 15 indicates.

:2 on the scale the button 19 is pressed to bridge the resistance coil 29 across the line conductors, whereby the vertical steps cease and a rotary impulse occurs at the selector to rotate. the shaft Wipers into contact with an idle trunk line leading to a connector switch H (Fig. 2). The conhector switch then operates to carry its-shattwipers into contact with the bank contact-s corresponding tothe line #220.

hen the'receiver is removed from the switch hook and ,t'hebutton 181 is pressed and released, and when the springs 24 and 26 and 21 and 22 engage, theeuergizing circuit for the line'relay 32 extends from ground G to the springs 34 and 37. line conductor 11, springs 24 and 26, magnet transmitter 7, primary winding 6, through the springs 22'and 31, line conductor in to the springs 36 and 37, line relay 2-3;. relay springs 38 and 39 to the battery lead 40, thence-through battery 13 to ground G. The line relay 32, upon energizing, presses the springs 41 and 42 into Contact. As shown, the line relay 32'is sloW,acting--- that is, when once energized and the energiz ing circuit is then broken, the relay does not instantly return to normal positiolnlait "41 and 42 closes an energizing remains in its energized position for a short nterval. The engagement of the springs circuit through the trip or plunger magnet 3 which latter operates to attract the plunger bank terminal.

arm 43 and thrust the plunger into an idle The plunger magnet .ci1'- 'euit extends from ground G through the springs 41 and 42, plunger magnet 33 to the battery lead 40, thence through battery B to ground G. \Vhen the plunger enters the bank terminal and closes the bank springs 44 and 45 in contact, an energizing circuit is established through the motor magnet relay 46 which latter operates to close thesprmgs 47 and 48 in contact, there-- by closing an energizing circuit through the motor magnet 49 of the master switch D. The motor magnet then operates toadvance all idle plungersthat are in locked engagement with the plunger shaft, bringing-them opinoves the latter one step.

posite the nextidle bank terminals similar tov theone just engaged. The circuit through the motor magnet relay 41' extends batter lead 4(, thence through battery ll to ground G. The circuit through the mag net 49 extends from ground G to the motormagnet 49. interrupter springs 53 and b4.

relay springs 4? and 48 to the battery lead 40. thence through battery B and ground G. The motor magnet, upon energizing. attracts its armature 55 and the pawl 56 engages a tooth of the ratchet wheel 57 and Prior to this operation the spring 58 engages a notch of v the toothed wheel (30. and when the ratchet wheel 57 is given one step the spring 58 slides from the top oi the notch and engages this manner as long as the springs 58 and 59 remain in engagen'ient. 'll' hen the next succeeding tooth on the wheel (.39 advances far enough the spring 58 discngages from the spring 59, thereby opening the energizing circuit for the motor magnet... By i'he'tiine this last notch disengages the springs and 59, the master switch wiper '49 has passed' from the first contact point 51 to the second contact point 61., Suppose, howercr, that when the wiper ,49 en gages the individual contact ($1 there is a guarding potential present. In that event an energizing circuit is closed through the motor magnet relay 46, said circuit extending from the contact 61 to the wiper 49", common segment 50, through the winding of the relay 46 to ground G as previously traced. 'lhc motor magnet. rela again en ergizes and closes the circuit for the motor magnet. The motor magnetoperatc s as before, and the wiper .49 carried to the next contact and the next tooth of the wheel 60 operates the. springs 58 and 59. This op eration continuesas long as the wiper 49 continues to find contact segments with protecting potentials. It will be understood. of course, that when the motor magnet 49 thus operates. the plunger shaft and all.

lit]

plunger enters the bank terminal the followm s I'IIIO'S are ressed into contact; 62

'and 63, 6a and 65, 66 and 67. The engagement of-the springs 62 and 63 extends "the calling subscribers line conductor 10 to the trunk conductor 68, While the engagement of the springs 66 and 67 extends the line conductor 11 to the trunk conductor 69. These conductors 68 and 69 lead to the side switch wipers 70 and 71 of the first selector E. When'the line conductors 10 and 11 are thus extended to the first selector E an energizing circuit is established through the line relays 72 and 78 and private magnet relay 81. The relay 72, upon energriaing,v

closes the springs 74 and 7 in contact, and

the relay 73, upon energizing, carries the spring 76 out of contact with the spring; 77

to the battery lead it), thence through batteryB to ground G. The relay 81 thereupon energrizcs and separates the springs 87 and 88. The engagement of the springs 76 and 78 provides an energizing circuit for the bridge-cutoff relay 32 in series with the plunger magnet 33 of the line switch G;

This circuit extends from ground G to the side switch Wiper 83,. springs 76 and 78, conductor 84-, bank springs 85 and 64-, bridge-cut-oii' relay 82, plunger magnet 33 to the battery lead -10, thence through hattery B to ground G. The bridge-cut-ofi' relay 82, upon energizing, would operate to disengage the springs 36 and 37, 34. and 35,

thereby disconnecting the subscribers' line conductors from the line switch C had not the armature e3 already done so. The trip or plunger magnet also bein included in this circuit. retains the plunger arm 43 in an attracted position. and the plunger in the bank terminal. Thus it will be seen that the line switch C,'after being operated from the subscribers station, is maintained in its operated position by a groundconnection at the first selector E.

The foregoing is the condition of the central" ofiice switches after the calling subscriber removes his receiver from the switch hook, presses and rcleascs'the button 19, and before the sel ctor switch E operates for the vertical impulses. 'When the relay 7 2 energizes and closes the springs 74 and 75 in contact, an energizing circuit established through the vertical magnet 85 and the slow- ,actmg relay 86 inmuitiple.

This circuit extends from ground Gr through the side switch wiper 83, springs 76 and 78, springs 75 and 7 1, springs 89 and. 90, through the vertical magnet 85 and slow-acting relay 84 in multiple to thebattery lead 10, thence through battery B to ground G. The verti cal magnet 85 thereupon energizes and oper ates to raise the shaft wipers 91, 92 and 93 one step in a vertical direction. The slow acting relay 86, upon energizing, carries the spring 80 out of engagement with the spring 7 9 and into. contact with the spring 91. w hen the springs 79 and 80 disengage, the energizing circuit through the line relay 72 and the magnet 12 in series becomes broken, and the relay 72 restores to normal, permitting the springs 74 and 75 to disengage. hen the springs 80 and 91 engage, a new energizing circuit is established through the line relay 73, said circuitextending from ground Gr through the relay 73, conductor 92, through the springs 91 and 80, private magnet relay 81 to the battery lead 10,

thence through battery B to ground G. The

relays 73 and 81, therefore, remain in their energized position. It should also be ex plained that when the relays 72 and 73 energize, the magnet 12 at the substation A also energizes, thereby attracting its armature 13 and moving the ratchet wheel 14 one step, carrying the pointer 15 to the scale division marked 1. When the relay 7 2 de-energizes,

the springs 74 and disengage; also, the magnet 12, being deprived of its energizing circuit, restores to normal position. The disengagement of the springs 74 and 75 of the line relay 72 breaks the energizing circuit for the vertical magnet 85 and \the slowacting relay 86. The relay 86, therefore,

returns to normal position, k whereby the spring again engages'the spring 79, and the energizing circuit for the line relay 72, in serieswith the magnet 12 and the line relay 73, is again established. The relay 72, therefore, energizes and presses the springs 74 and 76 into contact, whereby the circuit through the vertical magnet and the slow-acting" relay 86 is again established. The magnet 85 operates the switch shaft one more step, and the relay 86breaks the circuit for the line relay 72 as before. The magnet 12 also operates the second time and the pointer 15 is moved over the scale to the division marked 2. This indicates to the calling subscriber that the selector switch has traveled two vertical steps, and that the shaft wipers 91 92* and have been raised to the second level, opposite the trunk line conductors which lead to the connector switch F.

It should be stated that if nccessary the relay 72 may be made slow-acting to any suitable degree.

The I subscriber at substation A then presses the button 19, whereby the spring 21 is carried out of engagement with the spring i 22 and'into engagement with the spring 20.

' magnet.

This operation breaks the circuit'through the magnet 12 and bridges the resistance coil 29 across the line conductors 10and 11.

lVhen this resistance enters the circuit in series with the line relays 7'2 and 73'and the private magnet relay 81, sufficient current high resistance to prevent enough current from flowing over this circuit to operate the release magcnt 99. The depression of the button 19 also disengages the dog 18 from the. ratchet wheel 14, thereby allowing the indicator 15 to be restored to normal position in the manfier explained in connection with Figs. 3, 4 and 5.

WVhen the button 19 is restored to normal pbsition sulticicnt current again flows to energize the relay 81, which thereupon operates to disengage springs 87 and 88, whereby the energizing circuit for the pri vate magnet 94 is broken.- The private upon energizing, operates the springs 89 and 90, so that when the relay 72 eiergizes after the button is pressed an impulse will not be transmitted to the vertical magnet 85. The private magnet, as is well known, upon energizing and deenergizing. permits the side switch to pass from first" to second position, whereby when the wiper 100 engages the contactipoint 101 an energizing circuit is established through the rotaryinagnet 102. The rotary magnet then opt-rates to rotate the shaft wipers 1. and 93 of the selector E into en gz'rgmneut .with the first contact of the secrind level of the selector banks, trmnWhich wmtaots it is assumed the trunk ling conductors 1 3. 1 -1- and 105 lead to the connector switch 'F (Fig. 2). If the first trunk line busy, however, and the wipers have to pass over busy contacts, then as soon as the private wiper 93 engages the first private bank contact the private magnet D-l is again energized and the side switch is locked in second position. The

energizing circuit for the said private mag wiper side switch wiper 100, contact point 107, then through the private mag net 94 and normal springs 96, 97 and 98,.

release magnet 00 to the battery lead 40,

. wiper 71,

thence through battery B to ground G. The private magnet 94, upon thus becoming' cnergiyed, locks the. side switch wiper 100 in ei'igagelnent'with the contact point 101, whereby the rotary magnet 102' will he energized step by step until the wipers are carried beyond the last busy trunk line. At the instant that the private wiper 93 leaves the last busy contact point the en: ergizing circuitthrough the private mag net 94 is destroyed, and as a result the s e-' lector side switch passes to third position. If there are no busy trunk lines the rotary magnet 102 releases the side switch to third position as soon 'as the wipers are carried into engagement with the first trunk line. As soon as the side switch passes to third position as stated. the subscribers line conductors 10 and 11 are extended to the trunk conductors 103 and 104 which, in this case, it is'assumed lcad.to the connector switch F. The extending of the line occurs, of course, as soon as the side switch wipers 70 and 71 engage the contact points 108 and 109, respectively. Also, when the side switch Wiper 106 engages the third-position contact point the guarding potential is established at the privatebank contact corresponding to the trunk line conductors 103 and 104 for protecting the said trunk line against interference by another calling subscriber. The wipers of the side switch are broad enough to bridge across the space between the contacts, so that the battery is not disconnected from the line while the side switch is movingfrom one position to the other. lVhen the subscribers line conductors are thus extended to the connector switch F an energizing circuit is established through the line relays 110 and lll'and private magnet relay 118 in the same manner in which the energizing circuit was established through the line re lays 72 and 73 and private magnet relay 81 of the selector switch E when the subscribers' line conductors 10 and 11 were extended to the trunk condutors 68 and 69 through the line switch bank. The circuit through the line relays 110 and 111 and' .private magnet relay-118 extends from ground G through the relay 111,'trunk conductor 104, shaft wiper 92*, sidie switch trunk conductor 69, thence through the substation A Q) the trunk cofiductor 68, as previously traced, side switch wiper 70, shaft wiper 91, trunk conductor 103, line relay 110, springs 110 and 117,

through the winding of the private magnet relay 118'to the battery lead 40, thence through battery B to ground G. The relay 110, upon energizing, closes the springs 112 and 113 in contact: the relay 11, upon energizing, separates the springs 114 and 11 5, and the private magnet relay 118, when {energized separates, the springs 119 and 120. 1g)

The engagement of the springs 112 and 113 provides an energizing circuit for the vertical magnet 121 and the slow-acting relay 122 in multiple. This circuit extends from ground G to the springs 112 and 113, springs 123 and 124, side switch Wiper 125,

thencethrough the vertical magnet 121 in rotary magnet 126 is included in the circuit with the slow-acting relay 122 it does not operatively energize, since-the said'magnet is of comparatively low resistance. The relay 1 however, energizes to separate the spring 117 from thespring 116 and carries the spring 117 into engagement withthe spring 127. When the springs 116 and 117 disengage, the energizing circuit for the line relay and the magnet 12 at the station A is broken. The relay 110 and the magnet 12 therefore restore to normal position. When the springs 117 and 127 engage, a new energizing circuit is provided for the line relay 111, said circuit extending from ground G through the relay 111, springs 127 and 117, private magnet rela 118 to the battery lead 40, thence throng battery B to ground Gr. The disengagement oi the springs 112 and 113, when the relay 110 restores to normal, breaks the energizing circuit for the veitical magnet 121 and the slow-acting relay 122. After almoment the slow-acting relay 122 restores the spring- 11? to normal engagementwith the spring 116, whereby the circuit is provided for the line relay 110 in. series with the magnet 12. of the substation A and the line relay 111, together-with the private magnet relay 118. The line relay 110*again energizes and places the springs 112 and 113 in contact, whereby a second energizing circuit is established through the vertical magnet 121 and the slow-a ting relay 122 as before explaincd. The vertical mzignet operates as before, and the shaft wipers 127,.128' and 129 are raised a second step and broug ht opposite the second bank level. The substation magnet 12,.upon energizing the second time, moves the pointer 15") opposite the number 2 on the scale, thereby. indicating to the subscriber that the connector switch has operated for the second digit 2 of the dc.- sired number.

As shown in the dramiugs, the magnet 12 at the substation will be energized and the pointer niovcd one step as soon as the but-- ton 19 is released after the first digit is called. In case the wipers of the selector E iao'ro position opposite the first bank level.

have to rotateover several busy trunks, this movement of the indicator would take place a short time before'the vertical magnet of the connector F is ener ized, and if the di it to be called were 1 te subscriber-1mg t press his button before the connector time to operate. This would not result if any other digit than 1 were called, because the magnet 12 at the substation would not be energized a second-time until the shaft of the connector had actuailybeen stepped up two steps. It will thus be understood that the possibility of the subscriber pressing his button too early may be entirely eliminated if the first levels of the connector banks are left blank, i. e-., have no line connectors, or, what amounts to the same thing, if the banks are so arranged that it requires two vertical steps of the shaft to raise the wipers to a such case there would .be no subscribers numbers whose tens digit is 1, and CODSB? quently there would be no dan er of the calling subscriber pressing his utton before the connector has operated the number of times indicated by the pointer.

After the pointer reaches the No. 2 position on the scale the button 19 is again pressed to stop the vertical impulses and to step the side switch from first to second position. Whenth'e button 19 is pressed the springs 21 and 20 engage, thereby bridging the resistance coil 29 acrossthe line conduc I tors 10 and-11. The relay 110' again energizes when the slow-acting relay 122 restores to normal position with the spring 117. in contact with the spring- 116, but with the resistance coil 29 bridged across the line conductors 10 and 11. in series with the line relays 110 and Ill-and the private magnet relay 1l8,. sullicientcurrent does not flow to maintain the relay in its operated position.

The springs 119 and'120 therefore engage and close, an energizing circuit through the breaks the euergizingcircuit for the private magnet 130.-- The private magnet, upon energizing and tic-energizing, permits the side sw tch wipers to pass from first to see 0nd position. Furthermore, when the but-- ton 19 is pressed the dog 18 is carried out of engagementwith the teeth on the ratchet wheel 14, and the spring 17 again restores the ratchet wheel 14 and the pointer 15 'to normal position. Afte'r theenergizing circuit through the private magnet 130 and the slow-acting relay 131 is broken the springs 123 and 124 engage, and an energizing circuit is now established through the rotary magnet 126 in multiple with the relay 122' and'thevertical magnet 121 in series. This circuit extends from ground (3' to the springs '112 and 113, springs 123 and 124, side switch wiper 125, contact point 136 to the rotary magnet 126, thence to the battery lead 40; also, from the contact point 136 through the slow-acting relay 122 and thei vertical magnet 121 in series to the battery lead 40, thence through battery B to ground G. The vertical magnet 121 being of comparatively low resistance does not operatively energize whenv in series with the relay 122. The slow-acting relay 122, however,

operates as before to carry the sprin 117 out of contact with. the sprin 116'an into contact with the spring 127, The disengagement of the springs 1 16 and 117, as

previously explained, breaks the energizingcircuit for the line relay and themagnet 12 of the substation A. The relay 110,

therefore, (ls-energizes and breaks the ener gizing circuit for the rotary magnet 126 and the slow-acting relay 122.' The slow-acting relay 122, after a short interval, also dc energizes and permits the spring 117 to engage the spring. 116, vthereby again restoring the energizing circuit for the line-relay 110 and the magnet 12, as previously ex-i plained. The energizing circuit for the rotary magnet 126 and the slow-acting relay 122 is again established when the line relay springs 112 and 113 engage. Thus the 'rota'ry magnet 126 is given two steps and the wipers 127, 128 and 129 are-carried onto the second contact of the second level. Also,

the pointer 15 of the substation indicating device now rests opposite the number 2, in-

dicating to the subscriber that two of the rotary impulses have operated at the counector. "When the relay 122 energizes, the

circuit for the line relaydlO and the magnet 12 is again broken. This intermittent energizing and de-energizing of the line relay 110 and the magnet 12 continues until the pointer 15 reaches the division indicated by O on .the scale. This indicates to the calling subscriber than ten impulses have been sent for the last digit O,'wheren the wipcrs 127,

128 and 129 have been carried into contact with the last bank contact points of the second level, from which'the normal conductors 137 and 138 lead to the line conductors of the called substation I The button 1.9 is again pressed, bridging the resistance coil 29 across-the line conduct tors 10 and 11, and again permitting the private magnet relay 118 to restore tog non I mal position, whereby the springs 119 aiid again engage and re-establish the en ergizing circuit for the private magnet energizes as before, permitting the side switch wipers to pass from second to third position. l-Vhen the side switch wiper 139 passes to third position a guarding potential is established 'at the shaft private wiper 129 for protecting the called line against seizure by some other calling subscriber.

This potential extends from ground through the side switch wiper 139 and conductor 140 tmthe shaft wiper 129. An energizing circuit is also established through the bridgeout-o-fl' relay 141 pt the line switch Q. This circuit extends from groundthrought'he side switch wiper 139 to the shaft wiper 129, conductor 142 to thebridge-cut-ofi' relay 141, to the tripior plunger magnet 143,-th enc to the battery lead 40, and through battery 13' to ground G. i The bridge-cut-ofi relay 141 I is of com arativ'ely high resistance, and the trip or p ung'fr magnet 143 does notoperatively ener 'ze when in normal position. The relay 141, upon energizing, operates to disconnect thenormal conductors 137 and 138 from the line switch C.

The subscribers line conductors 10 and 11 having been extended to the subscribers nor-' ma] conductors 137 and 138 through the condensers 144 and 143, the-calling subscriber now presses the button 19 to energize the ringer relay 146, whereby thetierminals of the ringer generator Hare bridged across the terminals of the called line to signal the subscriberat substation A, When the I button 19 is pressed the relay-118 again dethe springs 152 antli150, side switch wiper 153 shaft wiper l27',"not "mal conductor 137, line conductor 154, condenser 155 and ringer 156, springs 157 and 158 to the line conductor 159, normal conductor 138, shattwiper' 128, side switch wiper 160, then through the ringer relay springs 151 and 153 back to the ringer generator TI, Tn response to the signal the called subscriber removes the reccivcr from the switch hook and presses and releases the button 161; lVhen the button 161 is pressed the lock' 162 is carried out of v engagement with the switch hook 163, and the switch'hook rises, carr ing the springs 158 and 164 into contact, thereby closing the primary circuit for the-substation A. The transmitter 165 of the substation A is pro vided with battery current from ground G through the relay 166, through the ringer relay springs and side switch wiper to the normal conductor 138, line conductor-V159, springs 15S ahd 164, through the magnet 167, transmitter 165,. primary Winding 168, springs 169 and 170 to the line'conductor 154, normal conductor 137, through the shaft and side switch wipers, ringer relay springs and relay 171 to the battery lead 40, thence through battery B to ground G. The trans mitter 7 ofthe calling substation A is provided with talking current through the line relays 110 and 111 and private magnet relay- 113, as previously traced. The two substationsbeing thus cc nnected, conversation may be carried on over the conductors indicated by the heavy lines in Figs. 1 and 2.

The release of the central office switch ing apparatus is brought about by the ...subscriber who restores his receiver to the switch hook last. Suppose, for example, that, the subscriber at substation A has restored his receiver;-then the relays 171 and 166 restore to normal position, placing the springs 148 and 149 in contact. The release of the switches is thcn broug ht about when the. subscriber at substation A restores his receiver .to the switch hook. -Whenfthis occurs the springs 24 and 26 disengage, thereby breaking the energizing circuit which includesthe line relays 110, 111 and private magnet relay 11,8 of the connector switch F. When the switch book 3 reaches its lowermost position the locking member 23 passes over the top of. the switch hook 3, as shown in Fig. 2, and locks the switch hook in its downward position. 'Also, when the switch hook is moved about its pivot point 172 the rod 173 rotates the shaft 31 and carries the dog 18 out of engagement with the ratchet wheel 14. When the springs 24 and 26 disengage and break the energlzing circuit for the line relays 110, 111, and private magnet relay 118, as explained, the said relays restore to normal position, whereby the springs 114 and 115 now engage and close an energizing circuit through the release magnet 140 of the connector F in series with the release relay 171 of the selector switch E. This circuit eX- tends from ground (1 through the release relay 173*, side switch wiper 106, shaft wiper 93, conductor 105, springs 115 and 114, through the normal springs 175 and 176, release magnet 140 springs 148 and 149 to the battcry learl 40, thence through battery B to ground G. The releasema'gnet 140 attracts its armature and restores the'connector side switch to first position,

gagement of the sprin s 175 and 176 breaks 7.

the energizing circuit tor the release magnet 1 10. The release relay 173 of the selector switch E also energizes in series with the release magnet 1 10 and operates to close the springs 178 and 17 9 in contact, thereby closing an energizing circuit through the release magnet 99, said circuit extending from groundGr to the springs 1'78 and 179, release magnet 99 to the battery lead 40, thence through battery B to groundG. The release magnet 99 thereupon energizes, restoring the selector side switch and shaft wipers to normal position. When the shaft reaches norma-l osition the normal arm 1S0 upon its end isengages the springs 96, 97 and 98. When the selector side switch restores to normal osition the holding circuit through the brldge-cut-ofi' relay 82 and plunger magnet 33 is broken. It will be seenthat after the selector side switch passes to third position the holding circuit for v I the plunger magnet 83extends from ground to the side switch Wiper 100, contact point 181, conductor 84, bank 5 rings 65 and 64, bridge-cut-ofi' relay 82, p unger magnet 33 to the battery lead 40, thence through battery B to ground G. Now, when the side switch wiper 100 restores to normal position this circuit is broken and the relay 82 and release magnet 33 de-erergize, whereby the arm 43 restores to normal position, permitting the springs of the bank terminal to restore to normal. position. scriber thus, upon hanging his receiver 2 upon the switch hook 3, opens the primary circuit at the springs 24 and 26, whereby the line relay 111 of the connector switch F is de-energized, bringing about the release of the central ofiice switching apparatus, as explained.

If the calling subscribershould restore his receiver to the switch hook first, then the circuit for the release magnet 14:0 is closed in a somewhat different manner. It was explained that when a calling subscriber restores his receiver to the switch hook the lincrclay 111 de-energizes and perfnits'the springsll l and 115 to engage; but if the called subscriber at station A still has his receiver otl theswitch hook. thus maintaining The calling sub series with lhe lmek-release relay of the se-' lector switch 1) and produces. the release of the. central ofliee switching apparatus, as previously explained. 7

In the foregoing it has been pointed out how a subscriber might. operate the central otlice switches to establish connection with another snbscribe1."s line. Suppose. for example. that when the subscriber at substation A calls the subscriber 'at-station A the line is busy-that another subscriber has called station A. or t-he subscriber at substation A has made/:1 call to someothcr station. In either event. a guarding potential will be established at t re private bank contact in the connectoubank corresponding to the line of substation A. Then. after the connector switch F is operatedfor the last digit 0. and the push button 19 is pressed to step the connector side switch wipers from second to third position. an energizing circuit is established through the private magnet 130 and relay131. and the side switch is locked in second position. This is brought about as follows: When the button 19 is pressed the private magnet 130 energizes as before. and closes thesprings 182 and 183 and 184 and 185'iu contact. "When the springs 182 and 183 engage. a locking circuit is established for the private magnet 130 and relay 131. said circuit extending from the grounded private bank contact to the shaft wiper 129. conductor 140. side switch wiper 139. contact point 186 (bearing in mind that the side switch. is now .in second position) to the springs 182 and 183, private 111agnet 130 in multiple with. the relay 131 to the'hattery lead 40. thence through batterv R. to ground'G. 'The private magnet and relay 131 are thus energizedand the side switch is locked in second position. and the snbseribers line is not extended to the nor mal conductors of the desired line. The husysignal. however...is'given the calling subscriber. indicating this condition! The busy signal current passes from the secondary winding of the. busv machine Ito the springs 185 and 184. condenser 145 trunk conductors 104 and69. line conductor 11, through the substation ,A to. the line condoctor 10. trunk conductors 68 and 103. through the relay 110. springs 116 and 117. private magnet irelay 118 to the battery lead 40. thence to the secondary \vinding again.

"Ihe culling subscriber is thus notified that the desired line is now in 'use and, upon hanging up the receiver. brings about the release of the switches in the usual manner.

In regard to the action of the relay 86, it may be added that the springs are soadjusted that when the. relay is energized the spring 80 makes contact with the spring 91 before leaving the spring 797 Otherwise the circuit through the relays 7.3 and 81 would be momentarily broken each time the verconnection with the line i'or a long time. or

in case the subscriber is being annoyed by 'other subscribers. This accomplished by the. relays 166 and. 171 in connection with the button .161. lVhen the button 161 is pressed the high resistance is inserted in the line. circuit. whereby sutlicient current does not flow tohold the relay 166 in an operated position. It accordingly falls back and outs battery toan alarm or other device such as the lamp 198. which will attract the atton tion of the attendant to this connector.

From the foregoing it will be seen that I proride a system in which automatic trunking and connecting operations are accomplished without the provision of any means for transmitting impulses over the lines from the substations thereof. To the con trary the maR'eaIQd-break devices for transniitting the electrical impulses are located at the exchange or central stat-ion. and while these impulses are being transmitted over the line circuit, the latter remains closed at the substation thereof, the said substation being provided with devices for merely che king or stopping the transmission of impulses as soon as the automatic switch that is operatingin response thereto has reached a desired or predetermined point in its operation, which predetermined point always corresponds to a digit of the called. number. In this Way a selector always stops at a' level corresponding to a digit of the called number. and then rotates automatical- ]y to find an idle trunk in the predetermined .such time the system is operating automatically, and is not under the control of the calllng' SlllJSCllbBl'. This i's-also truewhen a connector is operating vertically, and is true While the connector is operating in arotary manner to find. the called line. All of the acts ot'the calling subscriber are merely for the purpose of stopping the switches. at the predetermined or desired points in their operations, and are not for the pin pose of causing the switches to operate, with the. exception, of course of the initial act of the subscriber whichtfcauscs the line switch to operate. The numerical switch, (o-wit, the selectors and connectors, are each adapted to automatically respond as soon as conncction is made therewith'that is to say, 5 the mere seizure of the idle trunk line causes the selector or connector at the other end thereof to begin to operate, and its operation continues until stopped or interrupted by reason of some positive act on the part of the calling subscriber, and not because the calling subscriberhas ceased to'do something. The indicator at the calling substation is responsive tothe vertical operations of the selectors, but not to thejrotary operations thereof. The said indicator is, however, re-

sponsive to both the vertical and rotary operations of the'eonnector, as previously explained'. Thusthe indicator at the calling substation responds and operates in synchronism with all of the numerical switch operations at the exchange or central station. The calling subscriber stops the indicator and the switch that is operating in synchronism therewith at a point in the operation thereof corresponding to the digit of '.the called number. As shown, the act of the subscriber which stopsthe operation at the required moment is performed after the requisite degree of operation has taken place, and the stoppage of the switching operation occurs simultaneously with the act of the subscriber. For the broader purposes of my invention, however, the act of the.sub-- scriber which stops the switch at the desired point in its operation may occur either before or after the said operation. As disclosed, the acts of the calling subscriber alternate with the successive operations of. the switches, and this is true regardless of whether the act of the subscriber for stopping the operation of the switch precedes or follows that operation i It will also be seen that by my invention I provide .a two-wire system-that is to say, a system which is freefrom operating grounds at the substations theredf-anwhich the subjg cribers lines are provided with non-numerical trunking switches, and in which proviatch is made whereby the taking down of the 9 receiver at the callin substation does not result in the seizure o. a trunk or trunk line at the central station. In this way, and notwithstanding that the switches are controlled over complete metallic line circuits, the call- 5 ing subscriber cannot take down his recei 'erand monopolize a trunk line for some time before completing the call. With my. improved arrangement no trunk line is seizeduntil after the calling subscriber has pushed the button and thereby started the operation ofthe system to extend the call toward the called subscriber. I In addition it will be seen that provision is made for enabling anal-led subscriber to signal an attendant'atthe excliange or cenand substation from whence'it came... Thus seize a trunk by the initial closure of a 1110- means for preventing this operation.

'said impulses alternating with the numerical the calling substation rcsponsivc to each forming a series ofnumerical'switch-ingoperations; one for each. digit-of the called tral station without disconnecting his line from the line of the calling SLll'JSClllMEl. In this way the called subscriber can always ascertain from where the call camc-that is to say, can always ascertain the number of the calling subscriber. This is of advantage for various. reasons, as, for example. in cast-s where one subscriber. annoys another by persisten'rly calling him up for no other reason. In such case, and with my improved ar- I rangemcnt, the subscriber thus annoyed may signal the attendant at the exchangc or central station without releasing the connect ion. The said attendant, upon communicating with the called subscq' iber, can then trace the call back through the exchange to the line any called subscriber always has it within his power to retain the connection and thcrcby ascertain from whence the call came. A calling connection is always released by the subscriber who hangs up his receiver last.

\Vhat I claim as my invention is:

' 1. In a two-wire or metallic circuit controlled trunking system, trunk lines, a switch for selecting a trunk, means at the substm tion separate from the switch hook normally tending to control saidswitch tocause it to tallic circuit by a calling subscriber, and? 2. In a telephone system. a line circuit. means for performing a series of numerical switching operations, one for each digit of the called number; to extend connection toward the called subscriber, devices at the' exchange or central station for transmitting impul'ses'over the line circuit to operate said means, and a controller mechanism by "the initial operation'of which the calling party stops the transmission of said impulsesin accordance with the digits of the called n1im' ber,-said mechanism being at rest while the impulses are being transmitted over the line, and the acts of the calling party for limiting switching operations at the exchange or central statio 3. In a telephonesystcm, meanshaving motion in two intersecting planes for performinga series' of numerical switching. operations, one for. each digit of the called number, toextend connection toward the called subscriber, a substation mechanism atswitching operation, operating in" sfiichronism therewith, and means the initialopera;- tion of which variably limitsthe operation of said mechanism, whereby the calling party controls the extent of said operatiops. 4. In a* telephone system, means for pernumbcr, toextend connection toward the called-subscr1be1',-a visual indicator operating in synchronism with each of said opcrw trons. and mechanism the initial operation oi which stops said indicator atnny point in its operation. whereby the calling party may ternating observe and control thesaid switching operations.

5. In a. telephone system, a series of switches. means for automatically operating said switches to extend connection toward the callcdsubscriber, and a mechanism'by the initial operation of which the calling )arty terminates the operation of each switch II] accorilance with a digit of the called number, said mechanism beingat rest during the actual operation of any switch, the actuation of said mechanism by the calling party alwith the operations of said switches. I

'6. In a telephone system, an automatic two-motion switch, a metallic line circuit; therefor, means at the switch foropening and closing said metallic line circuit tocause a step-by-step operation of said switch, and means by which the calling party controls the extent ofoperation of said switch after said switch has started in operation.

7. In a telephone trunking system. a metallic line circuit, an automatic snitch'haring vertical step-by-step motion to select a group and rotary motion to find an idle trunk in the predetermined group. tomaticmeans at said switch for controlling the two sides of said line circuit to cause the said vertical motion.

8. In a telephone system, a line circuit an automatic switch having verticalv stepby-- step .motion to select a group and rotary 'motion to find the called line in the predctermined group, and automatic means at said switch for controlling the two sides of the line circuit in series to cause the said vertical and rotary motion.

9. In a telephone system, subscribers metallic line circuits, automatic switches.

devices at the exchange or central station :for automatically controlling said metallic line circuits to cause the operation of said switches, indicating means at the substa trons responsive to each switching operation.

and means at the substations by which the subscribers control the extent of operation of said switches in accordance with the digits of called numbers.

i 10. In a. telephone trunking. system. trunk lines'dividcd into groups, means for auto .mutically selecting groups and means for selecting. an idle trunk in a prcdetcrmincd group. a line circuitautomatically cont rolled at the exchange or central station to cause the group-selecting operation, and means by which the callin'g'party controls the linecircuit to terminate said operation in accordance with a digit: of the called number after said switcl; has started in operation.

and an sides of the calling line in series to select the called line, and means for rch asing the oin ncct'ion controllable only by the subsrribcr who hangs up his receiver last.

12. In a telephone system, autonml it means controllable hy-thc'callinn subscriber for finding and cxtendin; connection to the line. of the called subscriber. means for relcasing controllableonly by the subscriber who hangs up his receiver last. a central sta-- tion signal responsive only to the called subscriber. and means for preventing a release of the connection when the called subscriber operates the said signal.

13. Ina system for cst'ablishiirg complete metallic talking circuits between calling and called subscribers. a line circuit. means for performing a series of numerical switching operations. one for each digit of the called number. to extend connection towards the called subscriber. devices at the exchange or central station for transmitting impulses over the line circuit to operate said means.

and a controller mechanism by which thc callingparty limits the said impulses in accordance with the digllts of the called munber. said mechan sm home atrest while the impulses arc beingtransmitted over the line. Y

and the acts'ot the calling party for lim tiing said impulses alternating with the nnmerical switching operations at the ex hange or central station. said system bcin;- controllablc over the two sides oi the subscribcrs line in serics.- 1

14. In a system for establishing complctc metallic talking circuits bctwccn calling and called subscribers. means-tor pcr'l'oriniuo' a series of numerical switching operations one for each digit oi the called number. to extend connection to aid the called sol ,scribcr. a substation mechanism responsive to each switching opcration. operating in synchronism therewith; and mcans for rariably hunting the operation of said mechanism, whereby the calling party controls the extent of said operations. said system lacing controllable over the two sides of the subscribers line in series.

lfulu a system for establishing complete metallic talkingcircuits hctn'ccu calling and called subscribers. means For [)(l'ltllll'llllfl' a .serics of numerical switching operations. one

i'or cach dicit ol' the called number. to e'.'\ tend connection toward the called subscriber". a visual indicator ()lltlliltlllfl ll] vsynchronism with each of said operations. and mechanisn'i for stopping said indicator at any point in itsopcration, whereby the calling party may observe and control the said switching opcrations, said system being controllable over the two sides of the subscribers line in series.

16. In a system for establishing completemctallio talking circuits between calling and calledsubscribers, a series of switches, means for 'automatically operating said switches to extend connection toward the called subscriber, and a. mechanism by which the calling party terminates the operation of each switch in accordance with a digit of the called number, sa-id mechanism being at rest during lhe'actual operation of any switch, the actuation of said mechanism bythe calling party alternating with the operations of said switches, said system being controllable over the two sides of the subscribers line in series. v

17. In a system for establishing complete metallic talking circuits between calling and called subscribers, an automatic switch, a line circuit therefor, means at the switch for opening and closing the line circuit to cause a step-by-step operation of said switch, and

means by which the calling party controls the extenoof operations of said switch, said system being controllable over the two sides oi the subscribers line in series 18. In a system for establishing complete metallic talking circuits between calling and called subscribers, a line circuit, an automatic switch having vertical step-by-step motion to select a group and rotary motion to find an idle trunk in the predetermined group, and automatic means at said switch for controlling the line. circuit to cause the said vertical 1notion,-saidsystembeing controllable over the two'sides of the subscrib ers line in series. I

19. In a system for establishing complete metallic talking circuits between calling and called subscribers, a line circuit, an automatic switch having vertical ste'p-by-step motion to select a group and rotary motion to find the called line in the predetermined.

group, and automatic means at said switch for controlling the line circuitto cause the said vertical and rotarymotiomsaidtystem being controllable over the two sides of the subscribers line, in series. I

20. In' a system for establishingcomplete metallic talking circuits between calling and called subscribers, subscribers line circuits, automatic switches, devices at the exchange or central station for automatically controlling said linecircuits, to cause the opera,- tion of said switches, and means at the substations by whichthe subscribers control'the extentof operation of said switches in ac cordance withthe digits of called numbers, said system being controllable over the? two sides of the subscribers line in series.

.21. In a system for establishing complete gnetallio talking circuits between calling and called subscribers, trunk lines divided into oration, and means by whichthe calling party controls the line circuit to terminate said operation in accordance with a digit of the called number, said system being controllablc over the. two sides of the subscribers line in series.

22. In a system of telephonic transmission between calling and called subscribers, a line bircuit, means for performing a series of nun'ierical switching operations, one for each digit of the called number, to extend connection toward the called subscriber, devices at the exchange or central station for transmitting impulses over the line circuit to operate said means, a controller mechanism by which the calling party limits the said impulses in accordance with'the digits of the called number, said mechanism being at rest while the impulses are being transmitted over the line, and the acts of thcalling party for limiting said impulses alternating with the numerical switching operations at the exchange or central station, and substation transmitters connected to receive talking current from the exchange or central station.

. 23. In a system of telephonic transmission between calling and called subscribers,

means for performing a series of numerical switching operations, one for each digitvof the called number, to extend connection toward the called subscriber, a substation mechanism responsive to each switching op]- eration, operating in synchronism therewit means controlled by the calli for variably limiting said switc ing operation whereby the calling partylicontrols the extent of said operations, and substationv transmitters connected to. receive talking current from the exchange or central station.

24, In a system of telephonic transmission between calling and called. subscribers, means for performing a series of, numerical subscriber switching operations, one for each digit of the called number, to extend connection towardthe called subscriber, a. visual indi-.

cator operating in synchronism with 'each of said operations, mechanism for stopping said indicator at any point in its operation, whereby the calling party mayobserve and control the .said switching operations, and substation transmitters connected to receive talking current from the exchange or 'ce'ntralstation. Y I 25.: In a system of telephonic transmission between calling and called subscribers, a series of switches, means for automatically op erating aid switches to extend connection toward t m called subscriber, a mechanism by which th'ecalling party terminates the I hetwecu calling and called subscribers, suboperation of each switch in accordance with a digit of the called number, said mechanism being at rest during the actual operation of any switch, the actuation of said mechanism by the calling party alternating with the op erations of said switches, and substation transmitters connected to receive talking current from the exchange or central station.

26. 'In a system of telephonic transmission between calling and called subscribers, a line circuit, an automatic switch having vertical step-by-step motion to select a group and rotary motion to find an idle trunk in the predetermined group,- automatic means atsaid switch for controlling'the .line'circuit to cause the said vertical motion, and substation transmitters connected to receive talking current from the exchange or central station. I

27. In a system of telephonic transmission between calling andcalled subscribers, a line circuit, an automatic switch having vertical step--by-step motion -to select a group and rotary motion to find the called line in the predetermined group, automatic means at said switch for controlling the line circuit to cause the said vertical and rotary motion, and substation transmitters connected to receive talking current from the exchange or ccntr'l station.

28. In a system of telephonic transmission,

scrihers line circuits, automatic switches, devices at the exchange or central station for automatically controlling the two sides of said line circuits in series to cause the operation of said switches, means at the substations by which the subscribers control the extent ol operation to said switches in accordance with the-digits of the called numbers, and substation transmitters'connected to receive talking current from the exchange or central station. v

29. In a system of telephonic transmission between calling and called subscribers, trunk lines d1 ,idedinto groups, means for automuticall y selecting a group and for selecting an idle trunk in a predetermined group, a

line circuit automatically controlled at the exchange or central station to cause the groupselecting operation, meansby which the calling party controls the line circuit totcrminate said operation inacco'rdance with a digit of the called number, and subs'trdion. transmitters connected to receive alliiug current from the exchange or central station. p

30. In a telephone system, an automatic selector switch provided with a'plurality of relays, the first and second of said relays being normally in bridge of theline circuit, a circuit includingthe winding-of the first relay in series with the winding .of the third relay, means whereby the first and fourth inlays cooperate to transiuit electrical impulses over the line circuit, a magnet at the substation, indicating means operated by said magnet in response to said. impulses. release mechanism for said selector, means r'or releasing said switch, and a resistance at the substation for preventing prematureiopciu- I tion of said release mechanism.

31. In a telephone system, an automatic connector switcli provided with 'means for finding .the called suhscribcrs line, a plu rality of relays for said connector, the first and second of said relays being liridgvd across conductors of the talking'circuit, a circuit including the winding of the first relay in series with a winding of the third relay, means whereby the first and fourth of said relays cooperate to transmit electrical impulses over the line circuit, a magnet at the substation, indicating means operated by said magnet inresponse to said impulses, release mechanism for said connector, means for releasing said switch, and a resistance at the substation for preventing premature operation of said release mechanism.

32. In a telephone system, a trunk line. an automatic switch,a relay for said switch included in a bridge across said trunk. an operating magnet and a slow acting relay controlled by said first mentioned relay,- and -means controlled by said slow acting relay. for controlling said first mentioned relay.

33. In a telephone system, an automatic switch, a relay for said switch, a magnet for controlling said switch controlled by said relay, and a slow acting relay controlling said firstnlentioned relay, which slow-acting relay in turn is controlled by said first i mentioned relay.

BLLIn a telephone system, a line circuit, an automatic switch, means for connecting said switch with said line circuit, apair of relays in bridge of said line circuit, a third relay in said bridge, an operating magnet for said switch controlled by one of said first mentioned relays, and means controlled by said third relay for preventing the operation of said magnet. Y

Ill) 35. In a telephone system, a trunk line,

an automatic switch, a relay for said switch included in abridge across said trunk, an operating magnet and a slow acting relay controlled by said first mentioned relay, means controlled by said slow acting relay for controlling said first mentioned. relay. and indicating'meansat the substation -responsive to the' operation of said switch.

36. In a telephone system, an automatic switch. a relay for said switch, a magnet for "controlling said. switch controlled by .said .relay. a slow acting relay controlling said first mentionedrelay, and indicating means at-the substation responsive to the operation of said switch. 7 v

37. In a telephone system, a line circuit. an automatic switch, means for connecting said switch with said line circuit, a pair.

of relays in bridge of said line circuit, a third relay in said bridge, an operating magnet for said switch controlled by one of said first mentioned relays, and means at the substation for controlling said third relay to prevent the operation of said magnet.

38. In a telephone system, trunk lines divided into groups, an automatic switch having motion in one plane to select a group and motion in a plane at right angles there-- to to find a line in a selected grou a relay for saidiswitch included in a bri ge across said trunk, an operating magnet and a slow acting relay controlled by said first men tioned relay, and means controlled by said slow acting relay for controlling said first mentioned relay. f s

39. In a telephone system, trunk lines divided into groups, an automatic switch havingmotion in one plane to select a group, and motion in a plane at right angles thereto to find a line in a selected group, a relay for said switch included in a bridge across said trunk, an operating magnet and a slow acting relay controlled by said first mentioned relay, means controlled by said\slow acting relay for controlling said first men tioned relay, and indicating means at the substation responsive to. the operation of said switch.

40. In a telephone system. lines divided into groups, an automatic switch having motion in one plane to select groups, and motion in a plane at right angles thereto -to line, an automatic switch having a vertical o find a line in a selected group, a relay for said sw1tch,'a magnet for controlling said switch controlled by said relay, and a slow acting relay also controlled by said first mentioned relay, which in turn is controlled by said slow acting relay 41. In a telephpne system, lines divided into groups, an automatic switch having motion in one plane to select groups, and motion in a plane at right angles thereto to find a line'in a selected group, a relay for said switch, a nagnet'for controlling said switch. controlled by said relay, a slow acting relay also controlled by said first mentioned relay, which in turn is controlled by said slow acting relay, and indicating means at the substationresponsive to the operation of said switch. N I

42. In a telephone system, lines divided into groups, an automatic switch having 1110-. tion in one plane to select groups, and motion' in a plane at right angles thereto to (ind a line in a selected group, a pair of re lays in bridge of said line selected. a. third 5 relay in said bridge, an operating magnet 'l'or said switch controlled by one ot said first mentioned relays and incans'at the substation for controlling said third relay to prevent the operation of said magnet.

operation of said operating lines divided intogrou s, a. selector switch having motion in one p ane to select groups, and motion in a plane at'right anglesthereto to select a line in a selected group, a line relay and a. slow acting relay a'da tedto control the said vertical motion, an means controlled at the substation for preventing this operation. P

44. In a. telephone system, subscribers lines, a selector switch having a vertical step-by-step motion adapted to extend connection from a callin subscribers line'to a called subscribers line, a. line relay in said selector, a magnet for controlling said step-by-step motion and a slow acting relay connected in multiple circuits and controlled by said line relay, means for energizing said line relay and thereby energizing said vertical magnet and slow acting relay, and means 43. In a telephone system, subscribers 45. In a telephone system, subscribers linesdivided into groups, an automatic switch having motion in one plane to select groupsand motion in another plane to find a line in a selected bridged across said inc, :1 third relay included in said bridge, a-side switch controlled by -said third relay, an 0 rating magnet controlled b saidpair o relays, and means'controlle at the substation for controlling said third relay to prevent the magnet. 46. In a telephone system, a subscribers step-by-step motion, a line relay and a. slow acting relay forming a reciprocatin element to produceimpulses for raising 0 shift.

a magnet at the substation responsive to Said impulses, and a resistance at the substation adapted to be bridged across the line to I prevent the operation of said rela s. 47. In a telephone system, I an said central oflice, means whereby it called cap, a pair of relays subscriber can signal the central ofiice,

meansfor releasingsaid switches, and means for preventing the releasin of said switches until after the operation o said signal;

' 48. In a telephone system, subscriberslines, a central oilice, connector switches, means for operating the some, a pair of relays bridged. across thecalled line,.means whereby the subscriber can control said relays to operate a suitable s1gnal,- and means for preventingthe release of the switches until after the operation of said signaL' 49. Ina telephone system, means for 'set- ,ting up atalking circuit between a; calling and a calledsubscribers-line, a connector switch controlled exclusively over two sides of the talking circuit in series to select and seize the called line,-1nearis controlled by the lie calling subscriber for releasing said switch,

and means for preventing a calling subscriber from releasing said switch.

50. In a telephone system, a calling and a (Allfll line, means including a trunk line and a connector switch for connecting the subscribers on said lines in conversation, said connector living controllable over the two sides of said trunk line in series, and means for releasing said connector con- 10 trolled by whichever one of said subscribers who last replaces his receiver.

Signed by me at Chicago, Cook County; Illinois, this 28 day of July 1920.

OMER KTRBY. 

